1. Field of the Invention
The present invention relates to a viewing system; more particularly, a spherical viewing system.
2. Description of the Related Art
In an effort to operate more efficiently, it is desirable to perform some tasks using telepresence. Telepresence refers to providing visual or other types of sensory information from a device at a remote site to a user that make the user feel as if he/she is present at the remote site. For example, many businesses now hold meetings using telepresence. Telepresence is also useful for distance learning and remote viewing of events such as concerts and sporting events. A more realistic telepresence is provided to a user by providing the user with the capability to switch between views, and thereby mimic, for example, looking around a meeting room.
In the past, when several views were made available to a user, several cameras with different optical centers were used. Such a situation is illustrated in FIG. 1. FIG. 1 illustrates cameras 2, 4, 6 and 8 with optical centers 10, 12, 14, and 16, respectively. When the user decided to change views, he or she simply switched between cameras. In more sophisticated systems, when a user decided to change views, he or she was able to obtain a view from optical centers 10, 12, 14, or 16 as well as from additional optical centers 18, 20, 22, 24 or 26. Views associated with optical centers such as 18, 20, 22, 24, and 26 were obtained by using views from the two cameras nearest to the selected optical center. For example, a view from optical center 18 was obtained by using the views from cameras 2 and 4 and interpolating between the two views so as to simulate a view from optical center 18. Such procedures introduced irregularities into views. In addition, forming these interpolated views required a large amount of computational power and time, and thereby made this technique expensive and slow to respond to a user""s commands. This computational overhead also limited the number of users that can simultaneously use the system.
Other prior art discloses that the several views made available to a user can also be derived from a single wide-angle view that is created from multiple individual views captured by multiple distinct cameras. However, prior-art arrangements to create a single wide-angle view from multiple individual views have been unsatisfactory. In some arrangements, there is substantial parallax between the individual views, parallax that would lead to artifacts where the individual views would overlap or adjoin in any composite image; such artifacts are avoided in some cases by intentionally fragmenting the wide-angle view to have substantial gaps between individual images upon their display (e.g., U.S. Pat. No. 2,942,516). In some other arrangements, even though parallax between individual views may be minimal or absent, image artifacts remain and there is no suggestion on how to prevent these image artifacts from occurring where individual views would adjoin in any composite image (e.g., U.S. Pat. Nos. 3,118,340, 3,356,002, 4,890,314, 5,187,571). In some other arrangements, the number of individual cameras is limited to be no more than three and precise optical alignment of cameras and projectors is required to create a composite wide-angle image that is optical, rather than electronic, for all practical purposes precluding the use of such a composite image in providing multiple views to a user as described above (e.g., U.S. Pat. Nos. 2,931,267, 3,031,920, 4,890,314). Of particular relevance here are prior-art arrangements that use one or more mirrors with more than one camera to create a wide-angle composite image: One problem that has remained unaddressed in such arrangements is how to rid the composite image of image artifacts due to portions of individual images being captured off edges of mirrors (e.g., U.S. Pat. Nos. 2,931,267, 3,031,920, 3,118,340, 4,890,314, 5,187,571); further, even in those of such arrangements in which an attempt is made to reduce other image artifacts, which occur due to causes other than reflection off edges of mirrors and occur where individual images come together in a composite image, the arrangements and techniques proposed are limited to using no more than three cameras and are purely optical rather than electronic, requiring precise optical alignment of cameras and projectors and not lending themselves to providing multiple views to a user as described above (e.g., U.S. Pat. Nos. 2,931,267, 3,031,920). Some other prior art devices have no particular advantage with respect to acquiring a wide-angle field of view and also fail to avoid the above-mentioned image artifacts caused by portions of individual images being captured off edges of mirrors (e.g., U.S. Pat. Nos. 5,016,109, 5,194,959). These are just some of the drawbacks of the prior art that prevent it from being used to create high-quality composite wide-angle images that can be used to provide multiple views to a user as described above.
One embodiment of the present invention provides an omnidirectional or panoramic viewer where several cameras have a common optical center. The cameras are positioned so that they each view a different reflective surface of a polyhedron such as a pyramid. This results in each camera having a virtual optical center positioned within the pyramid. The field of view of each of the cameras is merged with the individual fields of view of the other cameras and arranged to form a composite field of view which is a continuous 360 degree view of an area when taken as a whole. The user can sweep through 360 degrees of viewing, where each view has the same or nearly the same optical center, by simply using the output of one camera or the combination of two cameras without requiring the computational overhead of interpolation used in the prior art. Such an arrangement may be used to enhance use of virtual meeting rooms by allowing a viewer to see the meeting room in a more natural format. This format corresponds closely to a person sitting in the actual meeting who simply turns his or her head to change the view at a particular time.
In another embodiment of the present invention, a nearly spherical view is provided to a user by placing a camera with its optical center at the common virtual optical center of the viewer. In order to enhance the spherical view, the camera at the common virtual optical center may use a wide angle lens.
In still another embodiment of the invention, the cameras are positioned so that their effective optical centers are offset from each other. The offsets produce narrow blind regions that remove image distortions received from the edges of the pyramid""s reflective surfaces. Additionally, planar shades that extend in an outward direction are positioned in the blind regions.
In yet another embodiment of the present invention, the viewing device may include any type of image transducer or processing device. If the image transducer or processing device is a camera or other type of image capture device, a panoramic or spherical image is captured for the user, and if the image transducer or processing device is a projector or other type of image producing device, a panoramic or spherical image is produced for the user.